Along with the trend in recent years toward compactness and high integration of semiconductor devices, the light sources for the fine working thereof are also under a trend of shift to shorter wavelength ones from traditional UV light to the g-line capable of forming a resist pattern of higher pattern resolution, from the g-line (436 nm) to the i-line (365 nm) and from the i-line to the KrF excimer laser (248 nm) to accomplish shorter and shorter wavelengths leading to the current ArF excimer laser (193 nm), F2 excimer laser (157 nm) and further electron beams such as EB and EUV shifter as a major current while developments of the process and photoresist materials are under progress at a high pace in order to comply with these short-wavelength light sources.
Conventional photoresists are required to have: for instance, improved sensitivity, pattern resolution, heat resistance, focusing depth latitude and cross sectional profile of a resist pattern to be obtained and improved aging stability resulting in the deterioration of the shape of the resist pattern due to contamination with an amine and the like in a period between light exposure and post-exposure baking (PEB) and controlled substrate dependency which changes are caused in the cross sectional profile of the resist pattern depending on various films provided on the silicon wafer such as insulating films including silicon nitride (SiN) films, semiconductor films including polycrystalline silicon (poly-Si) films and metallic films including titanium nitride (TiN) films. These requirements have been solved to some extent, but a defect which is a particularly important issue has many problems remaining unsolved.
The defect means a mismatch between a resist pattern and the photomask pattern, which is detected when a resist pattern after having been developed is examined from right above with a surface defect observation instrument, for instance, the mismatch like a difference between shapes of the resist patterns, occurrence of scums and contaminants, irregular coloring and coalescence between the patterns and the like. The yield of the semiconductor devices decreases as the number of defects increases so that, even though the resist has the adequate resist characteristics as described above, defects make it difficult for the semiconductor devices to be effectively mass produced, while the problems thereof remain unsolved.
While a variety of factors could be assumable as responsible for these defects, some of them include occurrence of microbubbles during development and re-deposition of insoluble matters once removed by cleaning.
As a method for decreasing such defects, a proposal is made (JP2002-148816A) to improve the formulation of the positive-working resist composition per se to be used for the pattern-formation but such a modification of the composition is undesirable because a modification of the process per se must be accompanied.
Further, a method is proposed (JP2001-23893A) for coating, in the course of resist-pattern forming, with a compound having a hydrophobic group and a hydrophilic group or, namely, with a surfactant but this method has defects that the top portion of the resist pattern is rounded to degrade the orthogonality of the cross section and, in addition, film thickness reduction of the resist layer is caused by this treatment. Moreover, this method requires due selection of the surfactant which must be in good matching with the resist used while, since it is usual in semiconductor processing plant, that the developer solution is supplied through collective pipings in the step of development, this method is inapplicable in a plant using, any kinds of resists necessitating changes of the treatment agents and washing of the pipe lines corresponding to each of the resists.
Furthermore, there are known a method for decreasing the defects in the developing step of photolithography by using a developer solution containing an organic base free from metallic ions and containing a nonionic surfactant as a principal ingredient (JP2001-159824A) and a method for decreasing the defects by conducting a treatment prior to the post-exposure baking treatment by using an aqueous solution of pH 3.5 or lower containing a low-volatile aromatic sulfonic acid and having a molecular weight of at least 200 (JP2002-323774A) but no satisfactory effect can still be reached.
On the other hand, a method of using the composition of a rinsing agent containing a nitrogen-containing compound with a molecular weight of 45 to 10,000, which has an amino group or an imino group, and a hydrocarbon group with 1 to 20 carbon atoms in the molecule, so as to inhibit falling and damage on a resist pattern occurring in a rinsing step and a drying step (JP11-295902A) is also known, but the method of using such a composition of a rinsing agent cannot reduce the above-described defects. Besides, a rinse solution containing an ethylene oxide-based or propylene oxide-based activator (JP2004-184648A) is known, but such a rinse solution cannot inhibit pattern falling because the hydrophilic group has weak interaction with water.